How can I keep blender from freezing whenever I try to render or bake a somewhat heavy scene in my no good very bad computer?
The most likely reason for such a crash is running out of memory - and for what you describe as a simple scene you should not be running out of memory. 

In order to reduce the memory requirement for your scene you could try reducing the size of your textures, simplify your mesh, reduce the level of subdivision surface modifiers (there are separate settings for Preview and Render - check both) and check for other modifiers that generate geometry (for example, a Remesh modifier can easily become a problem if set too high).

Simplify the scene and objects until you get a working render and then start adding complexity again until you find the cause.